Electrical contacting element



2,166,248 crarcai. con-racemes ELEMENT Frans R. Hansel and Kenneth L.Eel-t, In-

dianapolis, End, assignors to P. R. Mallory & 60., Inc., finnapolis,lind., a corporation of Delaware No Drawing.

5 Claims.

It is the further object of the invention to provide contacts capable ofoperating on high frequency at heavy current values fwithout ob-Jectionable contact metal transfer.

Other objects of the invention will be apparent from the followingdescription taken in connection with the appended claims.

The present invention comprises a combination 'of elements, methods ofmanufacture and the product thereof, brought out and exemplified in thedisclosure hereinafter set forth, the scope of the invention beingindicated in the appended claims.

while a preferred embodiment of the inven-' tion is described herein, itis contemplated that considerable, variation may be made in the methodof procedure, and the combination of elements without departing from thespirit of the invention.

The present invention comprises an improvement in silver-refractorymetal contact elements and especially in contact elements formed of atleast 6@%- silver.

In a number of contact applications silver is mixed with refractorymetals taken from the tungsten-molybdenum group. These materials areusually prepared by mixing the powdered materials together, pressing themixture and hot or cold worlnng the pressed product into suitable forms,from which contacts can be prepared.

It has been found that binary combinations of silver with members of thegroup mentioned above, especially when prepared by treating attemperatures below the melting point of silver have a definite tendencytoward a preponderance of metal transfer from the anode to the cathode.

We have discovered that the addition of a third element having thealloying characteristics oi manganese to compositions of silvertungstenor silver-molybdenum or silver-tungsten-molybdenum greatly improves thealloying and decreases noticeably the transfer tendency.

Elements such as tin, zinc, cadmium, and copper will alloy with silveronly but not with the refractory constituents, such as tungsten andmolybdenum. Metals such as cobalt and iron alloy with the molybdenum andtungsten, but not with the silver. For this reason they do not performthe same function as a metal such as man- Application January 5', 1939,Serial No. 249,476

ganese. While manganese is essential, the other metals mentioned may bepresent as dilution elements. I

It has been found that it is possible to incorporate further additionalelements such as iron, cobalt, nickel, silicon, which also improve thealloys and reduce the transfer tendency.

It is possible to produce a much stronger combination that way becausethe third constituent will form an alloy with both silver and refractorymetals, cementing not only the silver particles but the refractoryparticles as well to a greater degree than is possible in the binarycombinations.

which tendency is very much exaggerated as the The contacts covered bythe present invention may be composed of the ingredients inapproximately the following proportion.

Per cent Manganese 0.1 to 30 Tungsten and/ormolybdenum; 1 to 40 BalanceSubstantially all silver While it has been noted that the improvement ininterparticle wetting increases with increased -manganese content to amaximum of approximately %,-it has been found that the greaterimprovement is accomplishedwlthin the range of the constituents aslisted below:

Per cent 30 Manganese ll. 1 to 20 Tungsten and/or molybdenum l to 30Balance Substantially all silver As a specific example of our new andpreferred compositions, we have found the following to give completesatisfaction:

Per cent A.Manganese 5 Tungsten 5 Silver Balance B.Manganese 10 Tungsten20 Silver Balance C.--Manganese 15 Molybdenum 15 Silver BalanceD.Manganese 10 Molybdenum, 10 Tungsten 10 Silver Balance It has beennoted by experimentation that refractory combinations consisting ofmixtures of tungsten and molybdenum or their compounds with silver tendto produce what can be termed a peak type material transfer duringoperation crease in active area rapidly increases the current density atthe point of contact until failure results by early fusion. a

As previously mentioned, manganese because of its characteristic ofwetting both the refractory and non-refractory constituent limits thistendency, producing in operation a transfer of material whose height isgreatly reduced and, at the same time, the diameter of the base isincreased so as to produce what might be termed a dome or dome typetransfer. This condition is highly desirable as .it materially increasesboth the life of the contact and the current value at which fusion willoccur.

Material of the present composition when 25 tested on aresistive-inductive load at 12 volts D. C. operating at a frequency ofapproximately 400 times per minute was found to have a cur- 'rent figurevalue between 40 to"'l0% ,more than other commercial silver refractorycombinations 30 of the prior art. As has been mentioned, combinations ofthe present application are not as readily susceptible to materialtransfer producing values of .012" in comparison to .04 on equivalenttests.

What is claimed is:

essential ingredients, silver and at least one of the elements tungstenand molybdenum to which has been added manganese in the quantitiesranging from 0.1 to 30%.

2. An electric contact member composed of a refractory metal base andsilver alloy containing 0.1 to 30% manganese.

3. An electric contact member formed of a bonded mass of refractorymetal powders selected from the group consisting of tungsten andmolybdenum impregnated with a silver alloy containing 0.1 to 30%manganese.

4. An electric contact element formed of 1 to 40% of a material selectedfrom'the group consisting of tungsten and molybdenum, 0.1 to 30%manganese and the balance substantially all silver.

5. An electric contact element formed of l to 30% of a material selectedfrom the group consisting of tungsten and molybdenum, 0.1 to manganeseand the balance silver.

FRANZ R. HENSEL KENNETH L. EMMERT.

5 1. An electrical contact member containing as-

